Saturday, November 28, 2015

Originally utilized for human operations withing cis-lunar space in the 2020s, the reusable LOX/LH2 fueled ETLV-2 now heads towards its first crewed rendezvous and landing on the surface of the martian moon, Phobos, in 2031.

by Marcel F. Williams

NASA suggest that the first human missions to Mars will occur sometime in the 2030s. While the Obama administration has merely suggested a Mars flyby for the first crewed interplanetary voyage, others have proposed much more ambitious early human missions near the vicinity of the Red Planet. One frequent proposal is for a crewed journey to the orbit of Mars. Such an orbital mission could also include landings on at least one or both of the martian moons: Phobos and Deimos.

However, any serious efforts to transport humans on multi-year interplanetary voyages has to resolve the inherent problems of enhanced exposure to cosmic radiation and major solar events. Also, the deleterious effects of long term exposure to a microgravity environment over the course of several months and even years has to be resolved.

Mass shielding habitat areas with at least 30 centimeters of water could protect astronauts from the dangers of major solar storms while also enabling multiyear round trip missions to Mars and Venus without excessive exposure to cosmic radiation-- even during solar minimum conditions. The deleterious effects of microgravity on the human body could also be eliminated or, at least, substantially reduced by transporting astronauts aboard rotating interplanetary vessels with twin counterbalancing habitat modules.

However, a water shielded spacecraft with rotating habitat modules would substantially increase the mass of a crewed interplanetary vessel. One way to compensate for the increase in vehicle mass would be to launch the interplanetary vessel from one of the Earth-Moon Lagrange points-- instead of from LEO. This could shave off at least 2.8 km/s of delta-v requirement for an interplanetary mission. Dumping the water shielding for the twin habitat modules just a few hours, or a few days, before final trajectory burns into orbit could also substantially reduce the propellant requirements for an interplanetary vehicle. Finally, utilizing pre-deployed propellant producing water depots supplied with water from the Moon's low gravity well could also substantially reduce the propellant requirement for a reusable interplanetary vehicle.

In 2030, under this scenario, eight American astronauts and four foreign astronauts will depart from Earth-Moon Lagrange point four (EML4) towards a flyby of the planet Venus and then, a few months later, into high Mars orbit. During the interplanetary mission, astronauts will visit both of the martian moons, Phobos and Deimos, returning to Earth after the 22 month mission with a significant tonnage and variety of regolith samples from the moons of Mars. Water exported from the surface of the Moon from one of the lunar poles will be used to provide the water and propellant needed for the interplanetary mission.

Propellant producing water depot (WPD-LV-5A) on the lunar surface next to a mobile water tanker, LOX/LH2 cryotanker, and a Water Bug mobile microwave water extraction robot.

Nomenclature:

ETLV-2 (Extraterrestrial Landing Vehicle): Reusable LOX/LH2 vehicle capable of landing crews on the surface of the Moon or on the moons of Mars.

CLV-5B: Cargo
landing vehicles originally utilized to land large payloads on the lunar
surface but that are later utilized as reusable water tankers by
latching a water bag to the top of the spacecraft.

CLV-5A:
Reusable cargo landing vehicle specifically designed to transport water, regolith, or other heavy cargo from the lunar surface to the Earth-Moon Lagrange points.

February 2031: OTV-400 trajectory burn places Odyssey into a high Mars orbit.

February, March, and April of 2031: Two crewed ETLV-2 missions to the martian moon, Deimos and two crewed missions to the surface of Phobos

April 2031: OTV-400 trajectory burns transports Odyssey spacecraft from high Mars orbit into an Earth transfer orbit.December 2031: OTV-400 trajectory burns places the Odyssey spacecraft back into a halo orbit at EML4.

Maximum radiation exposure during the 18 month mission during solar minimum conditions (under 30 cm of water shielding aboard the Odyssey and including 10 days of temporary full exposure during orbital insertion and ETLV-2 visits to Phobos and Deimos): less than 50 Rem.

CLV-5A water tanker capable of transporting more than 50 tonnes of lunar water to the Earth-Moon Lagrange points. Mobile water tanker and a mobile LOX/LH2 cryotanker are near the shuttle spacecraft.

Cis-Lunar Space

During the early 2020s, a series of SLS cargo launches will be utilized to deploy a water and propellant producing and exporting infrastructure at one of the lunar poles . So starting in 2026, this will allow NASA to to focus its priorities on deploying the interplanetary infrastructure that will be necessary to take humans to the orbit of Mars in 2031-- and eventually to the surface of Mars in 2036. Under this scenario, the interplanetary infrastructure needed to accomplish these goals will mostly be derived from the technology and infrastructure developed for the cis-lunar program.

CLV-5A rendezvous with WPD-OTV-400 at EML4 to transfer more than 50 tonnes of lunar water. The orbiting depot will be capable of storing up to 1000 tonnes of water and up to 400 tonnes of LOX/LH2 propellant.

2030

Access to Orbit

In
February of 2030, three American Commercial Crew vehicles will
launch eight American astronauts plus four foreign astronauts from terrestrial launch facilities to low Earth orbit (LEO). All three of the Commercial
Crew vehicles will dock at LEO Way Station (LWS) that was originally deployed to LEO back in 2020. Simply derived from SLS hydrogen propellant tank technology and deployed by a single SLS launch, the LWS will be substantially cheaper than the hyper expensive ISS laboratory.

Rather than outsourcing technological participation from foreign space agencies, NASA will charge foreign space agencies $150 million for each foreign astronaut trained to participate in
NASA's first interplanetary mission. So the inclusion of four foreign astronauts in the interplanetary mission will shave off $300 million in cost to NASA-- and the tax payers. Foreign space agencies whose astronauts are participating in the Mars orbital mission
will receive up to 10 kilograms of material retrieved by astronauts and robots from the surfaces
of the martian moons, Deimos and Phobos.

An OTV-400 interplanetary booster rendezvous with a WPD-OTV-400 at EML4 to receive up to 400 tonnes of LOX/LH2 propellant. The WPD-OTV-400 produces propellant from lunar water when it is docked to a 1.2 MWe solar array (seen in the background) which is also located at EML4.

EML4

Docked at the LEO Way Station will be
two reusable ETLV-2 vehicles. Originally deployed by the SLS during the lunar outpost program of the early
2020s, each ETLV-2 vehicle will perform orbital transfer duties, transporting the international crew of 12 from LEO to EML4 ( Earth-Moon
Lagrange Point Four) in approximately two days at a slightly higher and more propellant expensive delta-v.

The LOX/LH2 propellant needed to fuel the
ETLV-2 vehicles will come from a LEO
orbiting propellant producing water depot (WPD-OTV-400). The LEO orbiting WPD-OTV-400 was
originally deployed by the SLS in the 2020's for cis-lunar operations.

WPD-OTV-400 depots will be capable of storing up to 400 tonnes of
LOX/LH2 propellant and up to 1000 tonnes of water. Some
of the water for the orbital depot will arrive as additional payload from Earth aboard SLS and other launch vehicles with some extra payload availability beyond the regular payloads that they will be deploying. But most of the water for the
LEO water/propellant depot will originate from the
surface of the Moon.

When running low on water and propellant, the LEO orbiting WPD-OTV-400
uses the remaining 50 tones of stored propellant to transport itself to EML4. There it
is supplied
with water and propellant from another WPD-OTV-400 that is continuously being supplied with lunar water from the lunar poles from reusable CLV-5A and CLV-5B water shuttles. Once the WPD-OTV-400 filled with 240 tonnes of water in addition to being fully fueled with 400 tonnes of LOX/LH2 propellant, it will redeploy itself back to LEO where most of the 240 tonnes of water will be converted into LOX/LH2 propellant. Large solar arrays deployed by previous SLS launched at both LEO and EML4 will provide all of the electricity necessary to power the depot electrolysis plants and cryocoolers for converting water into liquid hydrogen and oxygen.

The Odyssey

Once at EML4, the two ETLV-2
vehicles with dock at the twin AGH ports for the Odyssey interplanetary
vehicle, transferring the 12 astronauts to the vessel destined for
Mars. The Odyssey interplanetary vehicle consist of an OTV-400 orbital
transfer
vehicle capable of storing up to 400 tonnes of LOX/LH2 propellant; an
AGH artificial gravity habitat shielded with 30 cm of lunar water; and
two ETLV-2 crew transport vehicles with only 6 tonnes of propellant
within each vehicle. These Odyssey components will be deployed to EML4 by
three separate SLS launches the previous year (2029).

Inside
of the Odyssey, the 12 astronauts will be greeted by six others astronauts who are permanently stationed at an EML4 AGH
(Artificial Gravity Habitat) space station. The permanent artificial gravity space station is protected from
dangerous levels of cosmic radiation and major solar events with a
shielding of lunar iron slabs that were manufactured by 3D printers on
the surface of the Moon and exported to EML4 by reusable CLV-5A cargo
landing vehicles. The EML4 stationed astronauts will return to their AGH
space station after helping to prepare the crew of the Odyssey for their interplanetary launch.

Top: Odyssey trajectory burn configuration. 2nd from top: After the trajectory burn the OTV-400, AGH, and twin ETV-2 shuttles separate in preparation for vehicle reconfiguration. 3rd from top: After AGH shifts 90 degrees and then commences to rotate along an axis between the separated OTV-400 and the ETLV-2 vehicles. 4th from the top: AGH internal cables and external retractable booms expand to produce 0.5g of simulated gravity. Bottom: The two ETLV-2 vehicles rotate to match the rotation of the AGH before they dock with the structure at the pressurized central docking module.

Interplanetary Space

Since the Odyssey mission will take a longer route to Mars that will
allow it to also fly past the planet Venus, the OTV-400 will require
maximum amount of propellant. But launching from EML4 instead of LEO will still shave off nearly 2.8
km/s of its delta-v requirements. The WPD-OTV-400 will fill the Odyssey's OTV-400
with nearly 400 tonnes of LOX/LH2 propellant and its twin AGH habitat modules with more than 200 tonnes of water for radiation shielding (142 tonnes) plus water for drinking,
washing, food preparation, and the production of air.

Initially, the Odyssey will
be in a linear configuration when it departs from cis-lunar space. But
after the Mars Transfer Orbit trajectory burns, the Odyssey components will separate in order to
reconfigure itself so that the AGH can rotate and expand the light weight retractable booms surrounding the cables connecting its twin habitat modules. Extending about 112 meters away from the central axis while rotating at 2 rpm, each of the twin modules will experience a simulated gravity of approximately 0.5g. The astronauts within each habitat module would, therefore, feel a simulated gravity half that of being on the surface of the Earth but still significantly higher than the gravity experienced on the surface of the Moon or Mars. In theory, the artificial gravity environment should substantially reduce and possibly even eliminate the deleterious effects associated with microgravity environments. Artificial gravity should also
create a much more comfortable and familiar physical and psychological environment
during their 22 month mission.

In a trajectory configuration, the Odyssey flies past the plant Venus on its way to Mars.

Venus

In July of 2030, after nearly five months
of interplanetary travel, the Odyssey will reconfigure itself into a
linear configuration just a few days before it nears the planet
Venus. This will allow the OTV-400 to make some minor trajectory burns as they Odyssey flies past Venus on its way to Mars. During the flyby, the astronauts aboard the Odyssey could utilize one of the ETLV-2
vehicles to get a better look at Venus during the flyby, taking photographs and videos of the veiled planet. After the trajectory
burns, the Odyssey
will once again reconfigure itself so that the AGH can once again produce an artificial gravity environment for the astronauts.

After the AGH habitats dump their water shielding, the Odyssey reconfigures to a linear position in order to enter high Mars orbit.

2031

High Mars Orbit

Before the arrival of the Odyssey, two WPD-OTV-400 water/propellant depots will already be in high Mars orbit along
with a pair of large solar electric arrays, originally launched to high Mars orbit during the previous launch window in 2028.

In February of 2031, several hours to a few days before the Odyssey’s rendezvous with
Mars, the rotating AGH modules will dump their 142 tonnes of water shielding. This will cut the total inert mass of the
Odyssey nearly in half which will substantially reducing the amount of propellant required to
place the interplanetary vessel into a high Mars orbit. After the final trajectory burn places the Odyssey into orbit, the AGH will separate from the Odyssey to rendezvous with one of the WPD-OTV-400 water/propellant depots to replace the water shielding for its habitat modules.

Once the AGH modules are fully water shielded again, the Odyssey will reconfigure itself so
that the AGH can produce 0.5 g of simulated gravity and so that the crew can begin to conduct their exploration of the two martian moons.

The WPD-OTV-400, in high Mars orbit, rendezvous with the AGH to replenish the 142 tonnes of water for radiation shielding the habitat modules.

Fully water shielded again, the AGH begins to rotate again at 0.5 Gs, expanding its retractable boom and twin habitat modules.

Deimos

One of the ETLV-2 vehicles will dock
with one of the orbiting water/propellant depots in high Mars orbit,
accessing the amount of propellant needed for its crewed mission to the
surface of Deimos and back to the Odyssey. Six astronauts will participate in the three day exploration of the outer martian moon. After the astronauts land on the
surface of Deimos, a few mobile robots will be deployed that will be
teleoperated by astronauts still remaining at the AGH. For over a month, these robots will explore various regions on the surface of Deimos, taking videos and photographs and collecting samples. These samples will be retrieved a month later by the
second six person crew from the Odyssey to land on the surface of Deimos.

ETLV-2 on its way towards the first crewed landing on Deimos.

Phobos

After the first crewed mission to Deimos, Phobos will be the next destination for a crewed ETLV-2.
Again, six astronauts will participate in three days of exploration. After the astronauts land on Phobos, mobile robots will be deployed to explore various regions on the surface of of the inner moon, taking videos and photographs and collecting samples. These
samples will also be retrieved, a month later, by the
second six person crew from the Odyssey sent to the surface of Phobos

Preparations for Departure

After two
months in orbit around Mars, the
OTV-400 will fill its tanks up with more than 300 tonnes of
LOX/LH2 propellant from one of the WPD-OTV-400 water/propellant depots.

Reconfigured
into a linear configuration, the Odyssey will depart from Mars
in April of 2031. After the trajectory burns that launches the Odyssey into an Earth Transfer Orbit, the Odyssey will, once again, transform into an
artificial gravity producing configuration.

One of the nearly depleted
WPD-OTV-400 water/
propellant depots will also leave Mars for cis-lunar space in order to
resupply itself with lunar water and propellant for a return to Mars orbit in 2033.

With the solar power plant for the WPD-OTV-400 in the background, the OTV-400 rendezvous with the propellant depot to add LOX/LH2 for the Odyssey's return journey to cis-lunar space.

The Return to Cis-Lunar Space

In
December of 2031, the AGH will once again dump its water shielding as it nears its rendezvous with cis-lunar space. Once it is
linearly reconfigured, the final trajectory burns will place the Odyssey
and its crew back in halo orbit at EML4.

The crew will then be
transferred by two ETLV-2 shuttles to the EML4 AGH space station for a
few days before being transferred again by two ETLV-2 shuttles to LEO. Commercial Crew vehicles will then transport the astronauts to the Earth's surface, pioneers and heroes to be welcomed back by the cheering crowds on Earth.

The Odyssey interplanetary spacecraft returns to EML4. Two ETLV-2 shuttles docked at a permanent AGH space station at the Earth-Moon Lagrange point will transport the crew back to the EML4 space station for a few days before the 12 person crew is eventually transported to LEO and then back to the surface of the Earth aboard Commercial Crew vehicles.

The Next Interplanetary Mission

NASA, on the other
hand, will be preparing for the next crewed mission to Mars orbit which will be launched from EML4 in
2033. The 2033 mission will deploy the first permanent iron shielded AGH space station into high Mars orbit. The 2033 mission will also deploy the first unmanned
ADEPT protected ETLV-2 vehicles to the surface of Mars to test ETLV-2 s
ability to land large masses on the surface of Mars while testing the ability of the ETLV-2 to return to orbit from the surface of Mars.
Tele-operated robots will also be deployed by the ETLV-2 vehicles to retrieve regolith samples to
be transported to Mars orbit and eventually back to Earth.

"The knowledge that we have now is but a fraction of the knowledge we must get, whether for peaceful use or for national defense. We must depend on intensive research to acquire the further knowledge we need ... These are truths that every scientist knows. They are truths that the American people need to understand." (Harry S. Truman 1948).